U.S. patent application number 13/190838 was filed with the patent office on 2012-02-02 for electrical power supply system for an aircraft.
This patent application is currently assigned to Airbus Operations (S.A.S.). Invention is credited to Dominique Alejo, Cedric BAUMANN, Lucien Prisse, Julien Richer.
Application Number | 20120025604 13/190838 |
Document ID | / |
Family ID | 44041717 |
Filed Date | 2012-02-02 |
United States Patent
Application |
20120025604 |
Kind Code |
A1 |
BAUMANN; Cedric ; et
al. |
February 2, 2012 |
ELECTRICAL POWER SUPPLY SYSTEM FOR AN AIRCRAFT
Abstract
The invention relates to an electrical power supply system for
an aircraft comprising at least one main generator (20) feeding at
least one technical load and at least one commercial load through
at least one electrical power distribution channel comprising at
least one electrical distribution busbar (21, 23, 25) and at least
one voltage converter (22, 24, 26), wherein the grounding mode of
at least one load is an IT type grounding scheme, with an isolated
or high impedance neutral.
Inventors: |
BAUMANN; Cedric; (Toulouse,
FR) ; Prisse; Lucien; (Toulouse, FR) ; Richer;
Julien; (Toulouse, FR) ; Alejo; Dominique;
(Saint-Gauzens, FR) |
Assignee: |
Airbus Operations (S.A.S.)
Toulouse Cedex
FR
|
Family ID: |
44041717 |
Appl. No.: |
13/190838 |
Filed: |
July 26, 2011 |
Current U.S.
Class: |
307/9.1 |
Current CPC
Class: |
Y02T 50/54 20130101;
H02J 2310/44 20200101; Y02E 60/60 20130101; H02J 4/00 20130101;
Y02T 50/50 20130101; H02J 3/36 20130101 |
Class at
Publication: |
307/9.1 |
International
Class: |
B60L 1/00 20060101
B60L001/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 28, 2010 |
FR |
10 56193 |
Claims
1. An electrical power supply system for an aircraft comprising an
electrical network comprising at least one main generator (20)
feeding at least one technical load and at least one commercial
load through at least one electrical power distribution channel
comprising at least one electrical distribution busbar (21, 23, 25)
and at least one voltage converter (22, 24, 26), characterized in
that the grounding mode of at least one load is an IT type
grounding scheme, with an isolated or high impedance neutral, and
in that the high power technical loads use an IT type grounding
scheme, and the commercial loads use a TN-C type grounding
scheme.
2. A system according to claim 1, in which at least one load has a
TN-C type grounding scheme.
3. A system according to claim 1, in which the separation between
these grounding schemes is accomplished through the voltage
converters.
4. A system according to claim 1 in which the separation between
these two grounding schemes is accomplished through galvanic
isolation means.
5. A system according to claim 1, comprising a permanent insulation
monitor for the protection of the loads fed by the network using
the IT type connection scheme.
6. A system according to claim 1, comprising at least one AC
generator without a neutral connection.
7. An aircraft including a system according to any one of the
foregoing claims.
Description
TECHNICAL FIELD
[0001] The invention relates to an electrical power supply system
for an aircraft, for an airplane for example.
[0002] In what follows, for the sake of simplicity, an airplane
type aircraft is considered by way of example.
PRIOR STATE OF THE ART
[0003] In an airplane, the technical and commercial electrical
loads are fed by main and auxiliary generators through distribution
channels comprising electrical distribution busbars and voltage
converters.
[0004] In order to ensure the protection of goods and of persons
the ground connection mode in an aeronautical electrical power grid
uses a TN-C type scheme. This mode makes it possible to easily
ensure selectivity of the protections despite the large number of
loads connected. These loads can in particular be commercial loads,
the number whereof depends on the cabin accommodation selected by
the client company.
[0005] This TN-C type scheme means: [0006] T: neutral conductors of
the installation connected directly to ground, [0007] N:
installation frames connected to the neutral conductor, [0008] C:
installation frame protection conductor and neutral conductor being
coincident.
[0009] As illustrated in FIG. 1, in an electrical power supply
system on board an airplane, the neutral of each main generator G
is connected to the fuselage 10 of the airplane in order to ensure
a return path for unbalanced phase and fault currents. In addition,
all the frames of the different loads are connected to this
fuselage. The fuselage therefore plays the roles of neutral
conductor and ground at the same time. Thus, in FIG. 1 are shown a
three-phase generator G, the neutral whereof is connected to the
fuselage 10, connected to an electrical power center 11 by its
phases ph1, ph2 and ph3, a phase-to-ground fault load 12, the frame
of which is connected to the fuselage 10. A fault current id 13
relating to this fault load 12, which passes to the fuselage 10, is
also illustrated.
[0010] However, in such a TN-C type ground connection scheme, the
protections are triggered when the first electrical fault appears,
which is very prejudicial for the design of the technical
loads.
[0011] In the case of a "more electric airplane," connection of and
power supply to the loads is accomplished using distribution
channels such as that illustrated in FIG. 2. In this figure, a VFG
HVAC generator 20 is connected to an HVDC distribution busbar 21
through an HVAC/HVDC converter 22. This HVDC busbar 21 is connected
firstly to a DC distribution busbar 23 through an HVDC/DC converter
24 and additionally to an AC distribution busbar 25 through an
HVDC/AC converter 26. The DC distribution busbar 23 is connected to
a battery+charger set 27.
[0012] The requirements with regard to power necessitate the use of
a high distribution voltage, which allows the mass of the airplane
systems and of the cabling to be reduced. However, the commercial
loads and the calculators must still be supplied with 115 volts AC
and 28 volts DC for reasons of compatibility with existing
equipment. The power supply to these loads is thus accomplished
through converters.
[0013] The invention has as its object to resolve these problems by
using converters for accomplishing the separation of the electrical
grid into a "technical" part and a "commercial" part, the two parts
using different ground connection modes.
DESCRIPTION OF THE INVENTION
[0014] The invention relates to an electrical power supply system
for an aircraft, comprising at least one main generator feeding at
least one technical load and at least one commercial load through
at least one electrical distribution channel comprising at least
one electrical distribution busbar and at least one voltage
converter, characterized in that the ground connection mode of at
least one load is an IT ground connection scheme, with an isolated
or high impedance neutral, and in that the high power technical
loads use an IT type ground connection scheme and the commercial
loads use a TN-C type ground connection scheme, such a separation
being achieved for the purpose of protecting the loads.
[0015] Advantageously, at least one load has a TN-C type ground
connection scheme.
[0016] Advantageously, a separation between these two ground
connection schemes is accomplished through galvanic isolation
means, for example voltage converters.
[0017] Advantageously a permanent insulation monitor allows
protection of the loads supplied by the system using the IT type
connection scheme.
[0018] Advantageously the system of the invention comprises at
least one AC generator without a neutral connection, such a
connection having become unnecessary for the purposes of
protection.
[0019] The invention also relates to an aircraft including such a
system.
[0020] The system of the invention greatly facilitates protection
against short-circuits within the scope of a composite-built
airplane.
BRIEF DESCRIPTION OF DRAWINGS
[0021] FIGS. 1 and 2 illustrate two prior art arrangements.
[0022] FIG. 3 illustrates the system of the invention.
[0023] FIGS. 4 through 11 illustrate different features of the
system of the invention.
DETAILED DESCRIPTION OF PARTICULAR EMBODIMENTS
[0024] In the system of the invention two different modes of ground
connection are used, selected in the following fashion: [0025] The
high power technical loads use an IT type ground connection scheme,
that is with a neutral isolated from ground or having high
impedance, and the frames of these loads connected to the structure
of the airplane or to a conductive structure allowing current
return in the case of an airplane using thermoplastic composite
materials. Such an IT scheme is used in industrial installations
requiring continuity of service. It is, however, not used up until
now in the aeronautical field. [0026] The commercial loads use a
TN-C type grounding scheme.
[0027] The separation between these two grounding schemes is
accomplished through elements providing galvanic isolation.
[0028] Indeed: [0029] The high power technical loads, which operate
with a high voltage of 230 Volts AC or +/-270 Volts DC, need a high
level of availability and are not numerous; [0030] The commercial
loads and certain lower power technical loads, which operate at
voltages of 115 volts AC and 28 volts DC, are numerous.
[0031] In order to achieve the separation of a channel into a
"sub-network," as illustrated in FIG. 3, and to use the different
grounding schemes, a galvanic isolation is used between the
"sub-networks," achieved for example by the use of converters. In
FIG. 3 there are thus three sub-networks 30, 31 and 32 and three
converters, HVAC/HVDC 22, HVDC/DC 24 and HVDC/AC 26 respectively.
Indeed: [0032] The HVDC (High Voltage Direct
Current).rarw..fwdarw.DC voltage conversion can be accomplished for
example through a reversible BBCU (Buck Boost Converter Unit)
converter 40 having isolation stages 41 and 42, as represented in
FIG. 4. [0033] The HVDC .rarw..fwdarw. AC voltage conversion can be
accomplished for example through a converter 26 comprising an
inverter module 43 associated with a filter 44 which can include
isolation, as illustrated in FIG. 5. [0034] An HVAC (High Voltage
Alternating Current) .rarw..fwdarw. conversion can for example use
an ATU (autotransformer unit) transformer 45, which allows
isolation to be achieved, as illustrated in FIG. 6. [0035] An HVAC
.rarw..fwdarw. DC conversion can for example use a TRU (Transformer
Rectifier Unit) transformer-rectifier 46 and an isolation stage 47,
as illustrated in FIG. 7.
[0036] FIGS. 4 through 7 show converters using a delta-wye
connection. But it is possible to contemplate any other combination
of connections between primary and secondary, as long as they allow
isolation between the primary and the secondary.
Protection Using an "IT" Type Grounding Scheme
[0037] A high voltage "sub-network" can be protected by using an
"IT" scheme, which uses a permanent insulation monitor (PIM) to
protect the network. This monitor can be connected on the
alternating side or on the direct current side. In both cases,
fault detection works.
[0038] FIGS. 8 and 9 illustrate a protection using an "IT" type
grounding scheme in the case of a single fault or a double fault:
[0039] In the case of a single fault, the fault current is limited
by a high neutral-to-ground impedance. There is therefore no danger
and the fault is detected. [0040] In the case of a double fault, we
are dealing with a fault similar to a single fault in "TN-C" mode.
The same protective devices can then be used.
[0041] FIG. 8 illustrates a generator 50 comprising three stator
inductors, the neutral (common) point whereof is connected to
ground through a high impedance Z, sized so as to have a
non-hazardous fault current. This generator 50 can be connected to
the electrical network 51 through a three-phase switch 52. A first
load 53 can be connected to the electrical network through a
three-phase switch 54. A second load 55 is also shown. The line PE
represents the equipotential line of the connection of the frames
of the loads 54 and 55 to ground. When an insulation fault 56
arises, here on phase ph1 of the first load 53, a fault current id
circulates following the loop 57 and therefore passes through the
impedance Z, which limits the value of this current id.
[0042] In FIG. 9, the same elements are found as those shown in
FIG. 8. The second load 55 is now connected to the network through
a three-phase switch 57. When a double insulation fault arises,
here a fault 58 on phase ph3 of the first load 53 and a fault 59 on
phase ph1 of the second load 55, the fault current follows the loop
A, B, C, D, E, G, H, I, J, K, A, and does not pass through the
impedance Z.
[0043] The technical loads can be preserved in the event of a
single fault. Manual or automatic fault tracing then makes it
possible to determine the fault.
[0044] On a power channel, a permanent insulation monitor PIM 60 is
added as illustrated in FIG. 10.
Protection Using a "TN-C" Type Grounding Scheme
[0045] This protection scheme is widespread in the aeronautical
field. The electrical network is subdivided into multiple
sub-networks, each of which has an isolation transformer, the
secondary whereof has a distributed neutral. The neutral of the
transformer can be connected to ground and the frame of each of the
loads also connected to ground. We then have a "TN" type
scheme.
[0046] Such a design makes it possible to retain the simplicity of
implementation of this grounding mode and its natural ease of
operation with multiple loads.
Abnormal Operation
[0047] By "abnormal operation" is meant the loss of a generator and
the consequent takeover of a channel by another generator, as
illustrated in FIG. 11. In this figure, the channel already
illustrated in FIG. 10 is shown, and a second channel the reference
numbers whereof correspond to those of FIG. 10 with the addition of
a "'".
[0048] In this case, the permanent insulation monitor 60 of one of
the two channels is inhibited, the other permanent insulation
monitor 60' allowing the protection of the full network to be
accomplished.
Impact on Distribution
[0049] According to the subdivision of the electrical network that
is performed, the part of the network that is protected by an "IT"
type grounding scheme includes the generators. Thus, it is not
necessary to distribute the neutral of the generators, which then
makes it possible to simplify the installation and to reduce the
mass of the associated feeder line.
[0050] Further, the fact of not having a distributed neutral
eliminates by construction the voltage harmonics that are multiples
of three. New stator winding designs, allowing harmonics to be
limited, can therefore be used. Indeed, during the design of a
generator, the stator windings are arranged so as to minimize
harmonics which generate losses. As it is not possible to reduce
all harmonics, the choice often falls on suppression of the
harmonic of order 3, which requires a particular kind of winding.
In the invention, the elimination of the neutral makes it possible
to also eliminate any harmonic of an order that is a multiple of 3.
It is therefore possible to suppress or reduce any harmonic of
higher order, 5 or 7 for example, which allows the generator to
have fewer losses and therefore to be optimized as regards
efficiency.
[0051] In the case of an airplane made of thermoplastic composite
material (CFRP), as the neutral cabling can extend all the way to
the electrical power center, the contactor and the terminals
associated with this cabling can be eliminated.
[0052] The invention works no matter what kind of generator is
used: for example IDG (integrated drive generator), VFG (Variable
Frequency Generator) or even PMG (Permanent Magnet Generator), with
or without a starting function.
* * * * *